1. Field of the Invention
The present invention relates to the field of computer aided design (CAD). More specifically, the present invention relates to reusing subparts of one mechanical design in another mechanical design.
2. Background Information
Prior art CAD tools typically describe a mechanical design in terms of various geometric shapes, also referred to as “parts”. Each part in turn is expressed as a step-by-step recipe incrementally building the various features of the geometric shape, with each step roughly corresponding to a feature. In other words, each part is formed through a linear sequence of steps. For example, a linear step sequence may specify a particular geometric shape is to be formed by starting with a block, cutting a slot at a first location (a first feature), then cutting another angled slot at a second location (a second feature), and so forth. By changing the different design parameters of the “recipe”, different embodiments of the geometric shape may be built.
The prior art linear sequence approach to modeling geometric shapes of a mechanical design suffers from at least a number of disadvantages:                a) a significant number of topics or issues associated with the modeling of a mechanical design can not be expressed as features, e.g. equations to create cost, stress and so forth;        b) linear sequences are difficult to manipulate and re-order; and        c) linear sequences do not adapt well to reuse analysis, i.e. the reuse of a subpart of one mechanical design in another mechanical design.        
The fact that linear sequences do not adapt well to reuse analysis is especially problematic for CAD tools, as increasingly, mechanical designers desire to be able to reuse various subparts of their mechanical designs, in particular, the “standard” or “common” building block subparts employed in otherwise highly complex mechanical designs. Thus, a more effective and efficient approach to expressing mechanical designs and facilitating manipulation of the mechanical designs to allow different subparts of one mechanical design to be easily reused in another, is desired.